The proposed studies are designed to characterize and quantify secretion and metabolism of neurohypophyseal and pineal peptides, including arginine vasopressin (AVP), oxytocin (OT) and arginine vasotocin (AVT) in the fetus and newborn. The ontogenesis of neurohypophyseal (NH) secretion control systems, the role of NH peptides in the regulation of maternal-fetal water exchange, the specificity and maturation ofrenal and placental receptors for AVP and AVT, the maturation and significance of the circadian rhythms of AVP and OT in cerebrospinal fluid, the maturation of the AVT and melatonin rhythms in cerebrospinal fluid, the possible significance of AVT in pineal function, and the possible role of pineal AVT in the timing of puberty will be studied. The studies utilize sensitive and specific radioimmunoassay systems for measurement of AVP, OT and AVT in biological fluids and employ the chronically catheterized fetal sheep, the newborn sheep and adult sheep as animal models. The studies will be conducted inthe Perinatal Laboratories of the Departments of Pediatrics and Obstetrics and Gynecology at the Harbor-UCLA Medical Center. They are intended to characterize the role of the fetus in regulation of placental water transfer, the immaturities of pituitary function in the newborn as they relate to control of water metabolism and fluid and electrolyte management in the small premature infant, the maturation of circadian rhythms of hormone secretion and the control systems for daily hormonal rhythmicity, and the role of the pineal gland and AVT in modulating the onset of puberty and mediating precocious puberty in children.